Various members having a surface layer with various functions prepared by adsorbing functional fine particles on appropriate substrates have been proposed. Examples of the member having a fine particle-adsorbed surface layer include anti-reflection members with irregularity formed by fine metal particles, conductive members having conductive fine particles adsorbed thereon, anti-staining and antibacterial members having antibacterial metal (or metal oxide) adsorbed thereon, gas barrier films reducing gas permeability by utilizing fine particle-laminated structure and light shielding members using fine particle materials shielding ultraviolet ray, infrared ray or visible light.
As typical examples thereof, the roughened surface members having the specified fine irregularity are useful as materials for controlling the refractive index at an interface to prevent light reflection.
In recent years, image displays as typified by liquid crystal display (LCD), plasma display (PDP), cathode ray tube display (CRT) and electro luminescence (EL) lamp have been used increasingly in various fields, for example, television sets, computer machines and various mobile units which are becoming widespread recently. Such image displays have made prominent progresses. With improvement of the functions of various units using the displays, the demands of high-quality imaging and low electricity consumption toward the displays are increasing. For the high-quality imaging, anti-reflection property preventing reflection of light such as illumination on the display surface is an important element, along with the improvement of the pixel density in images and the achievement of bright color tone.
Particularly, since it is expected that displays for portable terminals which are becoming more widespread lately be obviously used outdoors, the demand of strong anti-reflection property preventing reflection of exterior light such as sunlight or fluorescent light on the display is increasing more than ever.
Additionally, LCDs of lightweight, compact size and versatility are broadly used. In the mobile units (portable terminals), the touch-panel input mode, namely an operation mode with direct touching of predetermined areas on the display surface with a plastic pen or fingers is frequently used. Not only image quality and anti-reflection property but also properties, for example, durability such as abrasion resistance and anti-staining property are now important for the display surface.
For the prevention of reflection, an approach to roughening the incident surface so as to scatter or disperse light has been ordinarily made in the related art. Treatment for roughening the surface include, for example, a roughening method of substrate surface directly with a sandblast process or an emboss process and a method for providing a surface roughened layer by coating a coating solution containing fillers on the substrate surface and drying.
Among them, the method for providing a surface roughened layer containing fillers on the substrate surface is commonly used currently from the standpoint of the controllability of the dimensions of irregularity on the surface to be roughened and the easy production of surface roughened layer.
For example, patent reference 1 (JP-A-6-18706 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”)) proposes a surface roughened layer comprising a UV-curing resin and a resin bead for the purpose of applying to highly transparent plastic film with poor thermal resistance.
A proposition using an inorganic pigment having good abrasion resistance such as silica instead of the resin bead is also made. However, such inorganic pigment is disadvantageous in its dispersibility, thereby causing a problem that a uniformly roughened surface layer is hardly produced. Therefore, for example, patent reference 2 (JP-A-11-287902) proposes a surface roughened layer using two kinds of pigments comprising silica and a resin filler having good dispersibility.
However, any one of these methods is a method of forming a surface roughened layer by coating filler for forming irregularity with a binder on a substrate. Therefore, the method has potentially a problem in that the level of the irregularity formed from the filler is reduced upon the influence of the binder, so that the anti-reflection property at the level as planned is hardly obtained. Further, when the binder is diluted or the amount of binder used is reduced for the purpose of improving the effect of filler on the irregularity, the strength of the resulting film is deteriorated so that it is likely to cause a problem of the durability.
As another method for forming an anti-reflection layer, a method of laminating alternately a material of a large refractive index and a material of a small refractive index to form a multi-layer construction is known. Specifically, the method for forming a multi-layer construction includes a vapor phase process of forming a film including alternately depositing a material of a small refractive index as typified by SiO2 and a material of a large refractive index such as TiO2 or ZrO2 and a sol gel process using hydrolysis and condensation polymerization of metal alkoxide.
Regarding these methods for forming anti-reflection layer of multi-layer construction, the vapor phase process using deposition requires a costly processing apparatus and involves difficulty in the production of anti-reflection layer of large size, while the sol gel process requires high production costs because of the repetition of the coating and baking procedures and additionally involves a problem in that stain is noticeable on the resulting anti-reflection layer because the anti-reflection layer is colored purple or greenish.    Patent Reference 1: JP-A-6-18706    Patent Reference 2: JP-A-11-287902